Process for producing binary or ternary graft-copolymer

ABSTRACT

A binary or ternary graft-copolymer excellent in both tensile strength and impact resistance is obtained by the process for producing a binary or ternary graft-copolymer consisting essentially of an ethylene-propylene rubber and an aromatic vinyl compound or of an ethylene-propylene rubber, an aromatic vinyl compound, and a vinyl cyanide compound, characterized by subjecting these materials to solution polymerization in a mixed solvent comprising an aliphatic hydrocarbon solvent capable of dissolving the ethylene-propylene rubber and a polar solvent capable of dissolving a poly-(aromatic vinyl compound) or a copolymer of the aromatic vinyl compound and the vinyl cyanide compound.

United States Patent Morimoto et al. Apr. 8, 1975 [5 PROCESS FORPRODUCING BINARY OR 3.657.395 4/1972 Meredith et al. 260/878 R TERNARYGRAFT COPOLYMER 3.671.608 6/1972 Meredith et al. 260/878 R 3.683.0508/1972 Meredith et al. 260/878 R [75] Inventors: Masayoshi Morimoto;Tetsutaro g i l fi l fi x l i l? Primary Examiner-Joseph L. Schofer yamad O C 1 Assistant Examiner-A. Holler [73] Assignee: Sumitomo ChemicalCompany, Attorney, Agent. or FirmStevens, Davis. Miller & Limited,Osaka. Japan Mosher [22] Filed: Jan.'29, 1973 [21] Appl. No; 327,316[57] ABSTRACT A binary or ternary graft-copolymer excellent in bothtensile strength and im act resistance is obtained by [30] ForelgnApphcatlon Pnomy Data the process for produclhg a binary or ternarygraft- Jan. 31, l972 Japan 47-l l727 copolymer consisting essentially ofan ethylenepropylene rubber and an aromatic vinyl compound or U-S. Cl.R; of an ethylene.propylene rubber an aromafic vinyl [5 lnt. rflpoundand a vinyl cyanide ompound haracter.

of Search R ized subjecting these materials to olution polymerization ina mixed solvent comprising an aliphatic hyl l References Cited drocarbonsolvent capable of dissolving the ethylene- UNITED STATES PATENTSpropylene rubber and a polar solvent capable of dis- 3.538.190 11/1970Meredith et al. 260/878 R 501mg Poll/(aromatic Vinyl Compound) orCOPOIY' 3.538.191 11/1970 Meredith et 111. 260/878 R mer 0f the aromaticvinyl Compound and the vinyl y- 3.53s.192 11 1970 Bishop 260/878 R anideompound. 3,538.l93 ll/l970 Meredith et al. 260/878 R 3.642.950 2/1972OShea 260/878 R Clam, N0 Drawmgs PROCESS FOR PRODUCING BINARY OR TERNARYGRAFT-COPOLYMER This invention relates to a process for producing athermoplastic resin excellent in impact resistance. More particularly,this invention relates to a solution-polymerization process forproducing a binary or ternary graft-copolymer consisting essentially ofan ethylene-propylene rubber and an aromatic vinyl compound or of anethylene-propylene rubber. an aromatic vinyl compound, and a vinylcyanide compound.

It has hitherto been attempted to develop a process for producing agraft-copolymer excellent in both impact resistance and weatherresistance by graftcopolymerizing styrene or styrene and acrylonitrileonto an ethylene-propylene rubber. in view of the fact that theethylenepropylene rubber is excellent in weather resistance. Most ofsuch processes has hitherto been known utilized a bulk polymerizationtechnique (U.S. Pat. No. 3,538,l92) or an emulsion polymerizationtechnique (US. Pat. No. 3,435,096), though a solution polymerizationtechnique has been used in some cases (U.S. Pat. No. 3,538,190).

However, although the graft-copolymers obtained by the above processeshave a weather resistance equal to or higher than that of, for example,an ABS resin due to the ethylene-propylene rubber used as a rubbercomponent, there still remains such problems that the impact resistanceof said graft-copolymers is generally inferior to that of an ABS resin.and even when there has been obtained, on rare occasions, agraft-copolymer having an improved impact strength, such a copolymer isinferior in tensile strength.

The present inventors achieved this invention as a result of extensivestudies to develop a graft-copolymer excellent in both impact resistanceand tensile strength by use of an ethylene-propylene rubber as a rubbercomponent.

An object of this invention is to provide a novel process for producinga well-balanced graft-copolymer having an excellent tensile strength andimpact resistance by binary or ternary graft-copolym erization from anethylene-propylene rubber and an aromatic vinyl compound, or from anethylene-propylene rubber, an aromatic vinyl compound, and a vinylcyanide compound.

Another object of this invention is to provide by the aforesaid processa binary or ternary graft-copolymer excellent in both tensile strengthand impact strength, and consisting essentially of an ethylene-propylenerubber and an aromatic vinyl compound or of an ethylenepropylene rubber,an aromatic vinyl compound, and a vinyl cyanide compound.

Other objects of this invention will become apparent from the followingexplanation and the description in appended claims.

The objects of this invention may be achieved by subjecting anethylene-propylene rubber and an aromatic vinyl compound or anethylene-propylene rubber, an aromatic vinyl compound and a vinylcyanide compound to solution polymerization to form a binary or ternarygraft-copolymer in a mixed solvent comprising an aliphatic hydrocarbonsolvent capable of dissolving the ethylene-propylene rubber and a polarsolvent capable of dissolving a poly-(aromatic vinyl compound) in thecase of the binary graft-copolymer, or of dissolving a copolymer of thearomatic vinyl compound and the vinyl cyanide compound in the case ofthe ternary graft-copolymer.

According to the process of this invention, there may be obtained agraft-copolymer which is well-balanced in impact resistance and tensilestrength, and which has favorable properties such as excellentextrudability and excellent surface gloss of the shaped articles.Moreover, the said process is characterized in that, as compared with aconventional process, the rate of graft-copolymerizationis markedlyhigher, the content of acetone-insoluble portion (a value proportionalto the conversion in grafting) is higher, and the molecular weight ofacetone-soluble portion (the main constitu ent being, for example, anacrylonitrile-styrene copolymer) is relatively large. The process has afurther advantage in that by varying the ratio between an aliphaticsolvent and a polar solvent, it is possible to control unrestrictedlythe rate of polymerization and the molecular weight of thegraft-copolymer.

The ethylene-propylene rubbers. as herein referred to. include not onlytwo-component polymers (hereinafter referred to as EPM) comprisingethylene and propylene, but also ethylene-propylene-diene terpolymers(hereinafter referred to as EPDM) containing as a third component such adiene as dicyclopentadiene. ethylidenenorbornene, l.4-hexadiene. 1.3-cyclooctadiene, 1,5-hexadiene, 1.7-octadiene, or 1,4- pentadiene. Anethylene-propylene rubber comprising ethylene and propylene in a molarratio of 5 l to l 2 is preferably used. In the case of EPDM, a preferredproportion of a diene component is 4 to 50 in terms of iodine value. Itis also possible to use the ethylene propylene rubber in combinationwith one or more of other rubbers; for instance. it is possible to useas a rubber component a blend of EPDM or EPM with one or more ofpolybutadiene, polyisoprene, and styrenebutadiene rubber. The blend ofthese different rubbers can be suitably selected according to thepurpose. However, when the purpose is to secure weather resistance.proportion of the ethylene-propylene rubber in the rubber component isgreater the better; for example, a preferred proportion is within therange from 50 to 100 by weight.

The aromatic vinyl compounds for use are styrene, a-methylstyrene,oz-chlorostyrene, and dimethylstyrene; among these, styrene is usedpreferably. As a vinyl cyanide compound, may be used acrylonitrile andmethacrylonitrile.

The weight ratio of these vinyl compounds to the rubber can be suitablyselected according to the purpose. Ordinarily, 5 to 20 by weight of arubber component is used for 95 to 80 by weight of a vinyl compoundmonomer. When a graft-copolymer is produced for the purpose of improvingcompatibility with other rubbers or resins, it is preferable forincreasing the degree of grafting to make weight ratio of the rubbercomponent to the vinyl monomer as large as possible; for example, asuitable proportion of the rubber component is within the range from 20to 90 by weight based on vinyl monomers.

In the case of a ternary graft-copolymer where an aromatic vinylcompound and a vinyl cyanide compound are used, the weight ratio of bothcompounds is adjusted within the range from 2 l to 5 l; for example, ina graft-copolymer involving styrene and acrylonitrile, a weight ratio of30 to 25 is most suitable.

The aliphatic hydrocarbon solvents, as referred to in this invention,should dissolve the ethylene-propylene rubber. Examples of such solventsinclude paraffins and cycloparaffins having to carbon atoms. such aspentane, n-hexane, 3-methylpentane. 2- methylpentane, 2,2- and2.4-dimethylpentane, heptane, cyclopentane, cyclohexan; cyclopentane andcyclohexane having alkyl substituents of l to 4 carbon atoms.

The polar solvents to be used in this invention may or may not dissolvean ethylene-propylene rubber, but should dissolve at least apoly-(aromatic vinyl compound) or a copolymer of an aromatic vinylcompound and a vinyl cyanide compound. Examples of suitable polarsolvents include ketones such as acetone, methyl ethyl ketone. methyln-propyl ketone, diethyl ketone. Z-hexanone, 3-hexanone, acetophenone,and propiophenone; esters such as methyl formate, ethyl formate, methylacetate. ethyl acetate, n-propyl acetate, n-butyl acetate, n-amylacetate, methyl propionate, and methyl n-butyrate; ethers such astetrahydrofuran and dioxane; chlorine-substituted aliphatic hydrocarbonssuch as dichloroethane and chloroform; nitrogencontaining hydrocarbonssuch as pyridine, aniline, acetonitrile, and dimethylformamide; andsulfurcontaining hydrocarbons such as dimethyl sulfoxide.

The solubility of a polymer in a solvent was qualitatively judged in thefollowing manner: A solvent was added to a polymer in an amount 10 timesthe weight of the latter at 25C. and the mixture was left standing for24 hours; on inspection of the mixture, the polymer was assumed to bedissolved when the mixture had formed a homogeneous phase or when thedegree of swelling of the polymer had exceeded 200 7: even if themixture had formed a heterogeneous phase.

Each one or more solvents selected from the abovementioned two groups ofsolvents are used as polymerization media in this invention. Forexample, a solvent system comprising one or more of the above-notedaliphatic hydrocarbon solvents and one or more of the above-noted polarsolvents may be used. A mixed solvent comprising 5 to 95 by weight of analiphatic hydrocarbon solvent and 95 to 5 7c by weight of a polarsolvent is ordinarily used. It is also possible to use only an aliphatichydrocarbon solvent in an initial stage of polymerization and add apolar solvent during progress of the polymerization. Best results areobtained particularly by using at the beginning of polymerization analiphatic hydrocarbon solvent containing 0 to 7t by weight of a polarsolvent and adding the polar solvent as the polymerization proceedsuntil the solvent system will contain in the final stage ofpolymerization 30 to 80 /0, preferably 40 to 60 76, by weight ofthepolar solvent. The rate of polymerization, the state of dispersion ofrubber, and the molecular weight of acetone-soluble portion in thegraft-copolymer can be freely controlled by regulating timing andquantity in adding a polar solvent as the polymerization proceeds. Asthe amount of the polar solvent increases, the rate of polymerization aswell as the molecular weight of acetone-soluble portion tend todecrease.

The catalysts to be used in the graft polymerization are common radicalpolymerization catalysts. Examples of suitable catalysts includeperoxides such as benzoyl peroxide, lauroyl peroxide, di-tert-butylperoxide, acetyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide,peroxybenzoic acid, tert-butylperoxypivalate and peroxyacetic acid, anddiazocompounds such as azobisisobutyronitrile.

In this invention, the catalyst can be added in portions. As comparedwith the addition ofa radical catalyst all at one time at the beginningof polymerization, the portionwise addition of the radical catalyst hassuch advantages as acceleration of polymerization, reduction inpolymerization time and improvement in physical properties of the endproduct. The vinyl monomer is added preferably also in portions, becauseit is possible, in this case, to obtain a polymer with a higher degreeof grafting and having superior physical properties as compared with thecase of adding as a whole.

The catalyst is used in an amount of 0.1 to 10 by weight on a vinylcompound monomer. The suitable polymerization temperature is 50 to 120C.The polymerization time depends to a great extent on polymerizationconditions, and it is desirably controlled so that conversion may reachor higher in 5 to 25 hours.

After completion of polymerization, the reaction mixture is poured withhigh-speed agitation into a lower alcohol such as methanol or ethanol toseparate a graft polymer in the form of powder. The separated polymer isair-dried and finally dried in vacuo at to C. for several hours. Thedried polymer is formed into pellets of suitable size by means ofapellet izer.

The graft-copolymer obtained according to this invention has a hightensile strength and an excellent impact resistance. A graft-copolymerobtained by the conventional process using n-hexane as thepolymerization solvent shows a microstructure, in which amicrophase-separation has occurred between the rubber component andother components, the interface of the two phases forming a distinctiveboundary between them, whereas the graft-copolymer obtained by theprocess of this invention using a mixed solvent as the polymerizationmedium shows a microstructure, in which the interface forms anindistinctive boundary. This fact seems to be the reason forimprovements in' dispersion of the rubber in the graft copolymer of thisinvention and in impact resistance of the graft copolymer. Further, thegraft copolymer of this invention has a high tensile strength which isin harmony with its excellent impact resistance.

The invention is illustrated below in detail with reference to Examples,but the scope of the invention is not limited thereto.

EXAMPLE 1 Into a 2-liter separable flask provided with a Dimrothcondenser, a thermometer, a glass tube for bubbling a gas, a Hopkinscooler and a stirring shaft with two turbine-type stirring blades, werecharged 50 g of EPDM having an iodine value of 18.7, a Mooney viscosityof 40, a propylene content of 34.7 by weight, and ethylidenenorborneneas a diene component, and 550 g of n-hexane. After thorough dissolution,to the resulting solution, were added 300 g of styrene, 100 g ofacrylonitrile and 2.4 g of benzoyl peroxide diluted with 50 g ofn-hexane. Polymerization was allowed to proceed under an atmosphere ofargon at 70C. while stirring with a stirrer revolving at 600 rpm. Whenconversion reached about 15 600 g of ethyl acetate was added dropwiseand the polymerization was carried out for 15 hours. After completion ofthe reaction, the graft-polymerization mixture was poured nto 5 litersof methanol to separate the polymer as a precipitate, which was driedunder reduced pressure at 150C. for 3 hours to obtain a graft-copolymer,12.7% by weight in rubber content. The copolymer was milled on a rollmill, 7 inches qS X 16 inches, at 170C. for 10 minutes. and pressed at200C. for 10 minutes to prepare a sheet. Dumb-bell-shaped testspecimens, JlS Pattern No. 3, were tested for tensile strength at roomtempera-' ture and at a stretching speed of 5 mm/minute. and lzod impactstrength according to ASTM D 256-56. The results obtained were asfollows:

Tensile strength: 520 kg/cm Notched lzod impact strength: 14 kg'cm/cmEXAMPLE 2 Polymerization was carried out for 15 hours in the same manneras in Example 1. except that a mixed solvent comprising 360 g ofn-hexane and 840 g of ethyl acetate was used. A graft-copolymer. 13.2 inrubber were measured in the same manner as in Example 1 to obtain theresults as shown below.

Tensile strength: 536 kg/cm Notched lzod impact strength: 12.6 kg-cm/cmEXAMPLE 4 The graft-copolymer obtained by the process of this inventionhas a markedly improved impact strength as compared with that of agraft-copolymer obtained by a known process (US. Pat. No. 3,538,190)using nhexane alone or a mixture of n-hexane and toluene. Examples ofmixing ratios by weight of n-hexane and ethyl acetate in mixed solventsrelative to elongation. impact strength and tensile strength of thegraft-copolymer are shown in Table 1.

These experiments were conducted following the procedure of Example 1,and only the solvent composition was varied, the rubber content of thegraftcopolymer having been regulated to be within the content, wasobtained, the physical properties of which range of 12 to 14 by weight.Elongation was meawere as shown below.

sured according to the method specified in HS K 6301.

Table 1 Run Solvent system Elon- Notched Izod Tensile No. (/1 by weight)gation impact strength strength Remark (/1) (kgcm/cm) (kg/0m n-Hexane100 Comparative l 7.2 8.7 523 Example Ethyl acetate 0 n-Hexane 70 3 8.010.6 526 Example Ethyl acetate n-Hexane 3 19.8 14.3 520 do.

Ethyl acetate 50 n-Hexane 40 9.6 21.2 458 do.

Ethyl acetate n-Hexane 30 5 1 2 24.0 375 do.

Ethyl acetate n-Hexane 50 Comparative 6* 7.0 3.2 530 Example Toluene 50A process described in [.15. Patent 3,538,190.

Tensile strength: 503 kg/cm Notched lzod impact strength: 24.0 kg'cm/cmEXAMPLE 3 1n the same polymerizer as used in Example 1, were charged 50g of EPDM having an iodine value of 9.7, a Mooney viscosity of 98, apropylene content of 43.5 "/0 by weight, and dicyclopentadiene as adiene component, and 550 g of n-hexane. After thorough dissolution, tothe resulting solution were added 300 g of styrene, g of acrylonitrileand 4.0 g of benzoyl peroxide diluted with 50 g of n-hexane.Polymerization was allowed to proceed under an atmosphere of argon at70C. While stirring with a stirrer revolving at 600 rpm. When conversionreached about 15 600 g of ethylene dichloride was added dropwise and thepolymerization was carried out for 32 hours. After completion of thereaction, the graft-polymerization mixture was poured into 5 liters ofmethanol to separate the resulting precipitate which was dried underreduced pressure at 150C. for 3 hours to obtain a graft-copolymer, 13.3by weight in rubber content. Physical properties What is claimed is:

l. A process for producing a binary or ternary graft copolymerconsisting essentially of an ethylenepropylene rubber and an aromaticvinyl compound or of an ethylene-propylene rubber, an aromatic vinylcompound and a vinyl cyanide compound, the ethylene-propylene rubbercomprising ethylene and propylene in a molar ratio of 5 l to 1 2 andbeing selected from the group consisting of two-component polymercomprising ethylene and propylene and ethylenepropylene-diene terpolymercontaining as a third component a diene selected from the groupconsisting of dicyclopentadiene, ethylidenenorbornene, 1 ,4- hexadiene,1,3-cyclooctadiene, 1,5-hexadiene, 1,7- octadiene or 1,4-pentadiene anda proportion of the diene component being 4 to 50 in terms of iodinevalue. the aromatic vinyl compound being selected from the groupconsisting of styrene, a-methylstyrene, a-chlorostyrene, anddimethylstyrene, and the vinyl cyanide compound being selected from thegroup consisting of acrylonitrile and methacrylonitrile, which comprisessubjecting these materials to solution polymerization in the presence ofa radical catalyst at a temperature of 50 to C for 5 to 25 hours in amixed solvent comprising to 95% by weight of an aliphatic hydrocarbonsolvent capable of dissolving the ethylene-propylene rubber and 95 to 5%by weight of a polar solvent capable of dissolving a poly-(aromaticvinyl compound) in the case of the binary graft-copolymer or ofdissolving a copolymer of the aromatic vinyl compound and the vinylcyanide compound in the case of the ternary graft-copolymer. thealiphatic hydrocarbon solvent being selected from the group consistingof paraffins and cycloparaffins having 5 to l0 carbon atoms,cyclopentanes having substituent alkyl groups of l to 4 carbon atoms,and cyclohexanes having substituent alkyl groups of l to 4 carbon atoms.and the polar solvent being selected from the group consisting ofketones. esters. ethers. chlorinesubstituted aliphatic hydrocarbons.nitrogen-containing hydrocarbons. and sulfurcontaining hydrocarbons.

2. A process according to claim 1, wherein the polar solvent is at leastone member selected from the group consisting of acetone. methyl ethylketone. methyl npropyl ketone. diethyl ketone. 2-hexanone, 3- hexanonc.acetophenone. propiophenone. methyl formate. ethyl formate. methylacetate. ethyl acetate. n propyl acetate, n-butyl acetate, n-amylacetate, methyl propionate. methyl n-butyrate. tetrahydrofuran. dioxane.dichloroethane. chloroform. pyridine. aniline. acetonitrile.dimethylformamide. and dimethyl sulfoxide.

3. A process according to claim 1, wherein the proportion of the polarsolvent in the mixed solvent is O to 7! by weight at the beginning ofpolymerization. the proportion being increased during the progress ofpolymerization by addition of fresh polar solvent, and reaches to 80 "/1by weight at the end of polymerization.

4. A process according to claim 1, wherein a blend of theethylene-propylene rubber with one or two of polybutadidne, polyisopreneand styrene-butadiene rubbers is used.

5. A process according to claim 4, wherein the blend containing theethylene-propylene rubber in a proportion of 50 to I00 by weight isused.

6. A process according to claim 1, wherein the aromatic vinyl compoundis styrene.

7. A process according to claim 1, wherein the ratio of the aromaticvinyl compound to the vinyl cyanide compound is from 2 l to 5 1 byweight.

8. A process according to claim 1, wherein the aromatic vinyl compoundis styrene and the vinyl cyanide compound is acrylonitrile.

9. A process according to claim 8, wherein the ratio of styrene toacrylonitrile is from 30 to 25 by weight.

10. A process according to claim 1, wherein the radical catalyst is atleast one member selected from the group consisting of benzoyl peroxide.lauroyl peroxide, di-tert-butyl peroxide. acetyl peroxide, tert-butylperoxybenzoate, dicumyl peroxide. peroxybenzoic acid, peroxyacetic acid,tert-butylperoxypivalate and azobisisobutyronitrile.

11. A process according to claim 1, wherein the polymerization isconducted in the presence of 0.1 to 10 by weight of a catalyst on thevinyl compound.

12. The process of claim 1 wherein said aliphatic hydrocabon solvent isat least one member selected from the group consisting of pentane,n-hexane, 2- methylpentane, 3-methylpentane. 2.2 dimethylpentane.2,4-dimethylpentane, heptane, cyclopentane, and cyclohexane.

13. The process of claim 1 wherein 5 to 20% by weight of saidethylene-propylene rubber is used with 95 to by weight of said vinylcompound.

1. A PROCESS FOR PRODUCING A BINARY OR TERNARY GRAFTCOPOLYMER CONSISTINGESSENTIALLY OF AN ETHYLENE-PROPYLENE RUBBER AND AN AROMATIC VINYLCOMPOUND OR OF AN ETHYLENEPROPYLENE RUBBER, AN AROMATIC VINYL COMPOUNDAND A VINYL CYANIDE COMPOUND, THE ETHYLENE-PROPYLENE RUBBER COMPRISINGETHYLENE AND PROPYLENE IN A MOLAR RATIO OF 5:1 TO 1:2 AND BEING SELECTEDFROM THE GROUP CONSISTING OF TWO-COMPONENT POLYMER COMPRISING ETHYLENEAND PROPYLENE AND ETHYLENEPROPYLENE-DIENE TERPOLYMER CONTAINING AS ATHIRD COMPONENT A DIENE SELECTED FROM THE GROUP CONSISTING OFDICYCLOPENTADIENE, ETHYLIDENENORBORENE, 1,4-HEXADIENE,1,3CYCLOOCTADIENE, 1,5-HEXADIENE, 1,7-OCTADIENE OR 1,4PENTADIENE AND APROPORTION OF THE DIENE COMPONENT BEING 4 TO 50 IN TERMS OF IODINEVALUE, THE AROMATIC VINYL COMPOUND BEING SELECTED FROM THE GROUPCONSISTING OF STYRENE, AMETHYLSTYRENE, A-CHLOROSTYRENE, ANDDIMETHYLSTYRENE, AND THE VINYL CYANIDE COMPOUND BEING SELECTED FROM THEGROUP CONSISTING OF ACRYLONITRILE AND METHACRYLONITRILE, WHICH COMPRISESSUBJECTING THESE MATERIALS TO SOLUTION POLYMERIZATION IN THE PRESENCE OFA RADICAL CATALYST AT A TEMPERATURE OF 50* TO 120*C FOR 5 TO 25 HOURS INA MIXED SOLVENT COMPRISING 5 TO 95% BY WEIGHT OF AN ALIPHATICHYDROCARBON SOLVENT CAPABLE OF DISSOLVING THE ETHYLENE-PROPYLENE RUBBERAND 95 TO 5% BY WEIGHT OF A POLAR SOLVENT CAPABLE OF DISSOLVING APOLY-(AROMATIC VINYL COMPOUND) IN THE CASE OF THE BINARY GRAFT-COPOLYMEROR OF DISSOLVING A COPOLYMER OF THE AROMATIC VINYL COMPOUND AND THEVINYL CYANIDE COMPOUND IN THE CASE OF THE TERNARY GRAFTCOPOLYMER, THEAIPHATIC HYDROCARBON SOLVENT BEING SELECTED FROM THE GROUP CONSISTING OFPARAFFINS AND CYCLOPARAFFINS HAVING 5 TO 10 CARBON ATOMS, CYCLOPENTANESHAVING SUBSTITUENT ALKYL GROUPS OF 1 TO 4 CARBON ATOMS, AND CYCLOHEXANESHAVING SUBSTITUENT ALKYL GROUPS OF 1 TO 4 CARBON ATOMS, AND THE POLARSOLVENT BEING SELECTED FROM THE GROUP CONSISTING OF KETONES, ESTERS,ETHER, CHLORINE-SUBSTITUTED ALIPHATIC HYDROCARBONS, NITROGEN-CONTAININGHYDROCARBONS, AND SULFURCONTAINING HYDROCARBONS.
 2. A process accordingto claim 1, wherein the polar solvent is at least one member selectedfrom the group consisting of acetone, methyl ethyl ketone, methyln-propyl ketone, diethyl ketone, 2-hexanone, 3-hexanone, acetophenone,propiophenone, methyl formate, ethyl formate, methyl acetate, ethylacetate, n-propyl acetate, n-butyl acetate, n-amyl acetate, methylpropionate, methyl n-butyrate, tetrahydrofuran, dioxane, dichloroethane,chloroform, pyridine, aniline, acetonitrile,
 3. A process according toclaim 1, wherein the proportion of the polar solvent in the mixedsolvent is 0 to 20 % by weight at the beginning of polymerization, theproportion being increased during the progress of polymerization byaddition of fresh polar solvent, and reaches 30 to 80 %
 4. A processaccording to claim 1, wherein a blend of the ethylene-propylene rubberwith one or two of polybutadidne, polyisoprene
 5. A process according toclaim 4, wherein the blend containing the ethylene-propylene rubber in aproportion of 50 to 100 % by weight is
 6. A process according to claim1, wherein the aromatic vinyl compound is
 7. A process according toclaim 1, wherein the ratio of the aromatic vinyl compound to the vinylcyanide compound is from 2 : 1 to 5 : 1 by weight.
 8. A processaccording to claim 1, wherein the aromatic vinyl compound is
 9. Aprocess according to claim 8, wherein the ratio of styrene to
 10. Aprocess according to claim 1, wherein the radical catalyst is at leastone member selected from the group consisting of benzoyl peroxide,lauroyl peroxide, di-tert-butyl peroxide, acetyl peroxide, tert-butylperoxybenzoate, dicumyl peroxide, peroxybenzoic acid, peroxyacetic acid,11. A process according to claim 1, wherein the polymerization isconducted in the presence of 0.1 to 10 % by weight of a catalyst on thevinyl
 12. The process of claim 1 wherein said aliphatic hydrocabonsolvent is at least one member selected from the group consisting ofpentane, n-hexane, 2-methylpentane, 3-methylpentane,2,2-dimethylpentane,
 13. The process of claim 1 wherein 5 to 20% byweight of said ethylene-propylene rubber is used with 95 to 80% byweight of said vinyl compound.